Pressure responsive device



" c. D. BRANSON PRESSURE RESPONSIVE DEVICE May 29, 1951 Filed May 15, 1946 Graven. for.

(Jim rles D-BMMOJL v I 1.! ll

attorneys Patented May 29., 1951 r PRESSURE, RESPONSIVE DEVICE .Charles D; Branson, Knoxville, Tenn; assignor to Robertshaw-Fulton Controls Company, a corporationof Delaware Application May 13, 1946, Seria'PNo; 669,439

3 Claims. -(Cl. 137-31565) This invention relates to pressure responsive .devices of the type employing an expansible and collapsible chamber that includes a .flexible wall that may be injured by excessive pressure.

:Pressure responsive devices including an-expansible and collapsible corrugated tubular. wall or :bellows having a movable end wall operatively connected toa means to be controlled and .associated with a relatively rigid wall enclosing the corrugated wall and providing therewith an expansible and collapsible chamber are wellknown in the art, said chamber sometimes, as in known forms of thermostat, containing a temperature responsive medium whose pressure varies with the temperature, but more commonly such chamher is connected through .anzinterposed .conduit with a source of pressure which may be a :bulb

containing a temperature responsive medium in the case of a thermostatic installation or such conduit may connect with any suitable .sourceof fluid pressure, whether liquid, vapor or gaseous, in other known forms of installation. .With structures of this character it is common practice to provide means for limiting the-extent of movement of the aforesaidmovable endwall, as by providing cooperating stop members in association with the operative connections between said movable end wall and .the'rmeans 'to be controlled, not onlyto avoid injury :to said :means to be controlled or the connections leading thereto in the event of excess pressure developing-in said expansible and collapsible/chamber,v but alsonto avoid fiexure of said corrugated wall to an extent that'said wall may. take azpermanent set orbecome otherwise injured due to-excessive flexure.

Expansible and collapsible corrugated tubular walls or bellows of the character referred to are commonly madeofm'etal on'the order of :fiveor six thousandths of an inch in thickness, and metal of this thinness is easily stressed by excessive pressures, which may result vin buckling or distortion of the wall, or, if the-wall is .not immediately deformed, the excess pressuremay develop large stresses per unit area which will result in a premature failure of the flexiblewall under repeated fiexure during the normal and intended operation of the device.

It is an object of this invention to-provide a device of the character described which automatically operates to :predetermine .the maximum pressure that :may'develop on'the flexible wall and thereby avoid the undue stresses generated therein which may result-in deformation or :premature rupture thereof.

Another object offthisinvention is to provide a device of zthe:characteridescribed with-means iorzprotectingthe flexible wall against excessive pressure which does-not1interfere with "the sensitive response of such wall. tosyarying; ;.pre s s 1;1r,e s within "the normal andintended range-ofbper tion of ;the device.

'Another object ref .thisg-invention is to provide a device :ofvthe. character ,described Wherein the means .for protecting the flex ble Wall;from excessive pressure. is simplein construction,:; .economical to.-produce andapplys and hi hly efiicient injoperation.

Other objects .of .thisginvention will appfiaras the description: of; therinvention; proceeds.

The invention is capable ofzreceiving ,a 1 variety of mechanical expressionsonly one; of iWhiGh'zhfi been :illustrated on the accompanying drawings, but itis tobeexpresslymnderstoodthat the .draw- 'ings are? for ,purposesof illustration only, and are not ;to.be construed as-a adevfinition oil the limits vof athe. invention, reference being' had the .appended,z-,claims for th tpurpo e- Referr-ing in: detail ato e-the: drawings wherein the same, reference: characters;,are.;emp1oyedin both figures ;to-;;designate corresponding ,parts,

. Fig- 1318313111 axi l:secti nhmantlv r aaway. andtsomewhat diagrammatic invcha-racter, ill-us- :tratinggan embodiment ofthe. invention; 1, and

xFig. g2 isua cross section taken on ,line@2- 2,; of Fig. 1; and looking in the' direction;ofv the arrows.

Referring ,in 1 detail ,to "thee-drawings, the .embodiment shown-pcomprisesan expansible and collapsible; chamber il 0: formed between .a generally "cup-shapedrigid ,wall; ll :of; any suitable sizeyconstruction,and material, and anex ansible and collapsible corrugated tubular; metal .walllor bellows l2j,1ilikewise of any-suitablesize, construction 1 and,omaterial ,1 said; all 12: being proadded with an end wall a ,l 3, integral therewith or suitably attached thereto; to whichis attached in any suitable wayzappropriate, .con ectionsi meansito be-.c,ontrol-led,;here isho-wn asiin the form of .a post :or red 1! 4;;attachedto; the end/w ll .l 3 by meansiofa. suitable fixture 1 5. .Aszis common in. structures. of; this character :the stationary,: end of the wall l 2 iszsuitablylsecured as.by. solderin or bra'Zing;.-.to an annular. plate; 5| Eaperturedat 11 toipermit free passagevof the rod or. posts and having its outer-periphery suitably; .zsecuned to the; open end ofzithe cup-shapedwwall l |',;&S::by spinning the open I end ;of said cupeshapedaawall I l around the external aperiphery for; the; plate 16, as shown at 18,..thejoint1between these two parts being 'preferably'lbrazedior' soldere sma sure a hermetic :joint. :Ataa! suitable ,epoint; in

said cup-shaped wall II a nipple I9 or other suitable connector is hermetically sealed into the wall and any suitable conduit, whether rigid or flexible and extending to any suitable distance, may communicate with a thermostatic bulb or with any suitable source of fluid pressure which,

by communication with said chamber III, will effect the expansion and contraction of said chamber to actuate the means to be controlled.

In conformity with the present invention means are associated with said expansible and collapsible wall [2 to predetermine the extent to which said wall may be collapsed under pressure and thereafter to seal said wall from any further increase in the actuating pressure so as to preclude injury of said wall by such increase in pressure after said means to be controlled has been moved to its limit position. To this end a generally cup-shaped shield 20 is mounted on the movable end wall of the bellows l2 and secured thereto in any suitable way, as by a projecting collar 2| on the fixture l which may be spun into locking relationship therewith as illustrated. If said shield is to perform no guiding function for the expansive and collapsive movements of the wall l2 its peripheral wall may have any suitable clearance with the cylindrical wall of the cup ll so as to assure that the actuating fluid may have free access to the interior of the shield 20. By preference, however, the shield aids in guiding the expansive and collapsive movements of said wall l2, and to this end an intermediate portion 22 of the peripheral wall thereof is made of ribbed, serrated or corrugated construction, as shown in Fig. 2, so as 'to provide channels for the free flow of fluid therepast while the tips of the ribs, serrations or corrugations have slidable contact with the inner surface of the cylindrical wall of the cup H so that the wall I2 is accurately guided in an axial direction as said wall expands and contracts. While reliance may be placed on the en- 'gagement of the extremity of the shield 20 with the end of the chamber to effect the sealing of the pressure in the chamber l0 away from the wall l2 when the latter has moved to its extreme position, a gasket 23 of any suitable material such as will not deteriorate under the action of the fluid in the chamber l0, neoprene for example, is preferably fixedly secured in position between the periphery of the plate IE or the end of the bellows secured thereto and a shoulder 24 on the cup II to provide a yielding seat for the edge 25 of the cup 20, said gasket also facilitating the making of a hermetic seal between the cup II and plate It.

The peripheral wall of the shield 20 is of such length axially that when the pressure in the chamber I0 has risen to such a value as, in conformity with the intended operation of the device, to cause the expansible and collapsible wall l2 to be contracted to that position in which the means to be controlled has been operated through the post or rod 14 to its limit position, the extremity 25 of said shield 20 will make a fluid tight engagement with the gasket 23 and thereby seal or isolate the space 26 within the shield 20 from any further increase of pressure in the chamber I0. Thus, as sometimes occurs in practice, the pressure in the chamber l0 may continue to rise because of a lag in the response to the repositioning of the controlling means, but with the present invention there is no increase of the pressure acting on the wall l2 after the latter has moved to a predetermined position corresponding to the limit position of the means to be controlled whereby said wall I2 is shielded from the excess stresses or deformation that would otherwise result from such increase in pressure. On the other hand, the pressure required to flex the wall I2 to its extreme position is trapped within the shield 20, so that as soon as the pressure in the chamber Ill decreases to a value below that required to flex the wall l2 to its extreme position the pressure internally of the shield will effect an expansion of the Wall l2 so that the latter will move the means to be controlled in the opposite direction at the required decrease in pressure as if no shield were present, thereby opening the chamber 26 inside of the shield 20 to the pressure in the chamber I0.

It will therefore be perceived that by the present invention a pressure responsive device employing a highly sensitive flexible wall is not only provided with means for predetermining the extent to which said wall may be collapsed by the actuating pressure, taking the place of the stop devices heretofore employed for preventing an excessive collapse of said wall, but as soon as said wall has been flexed to its limit position it is immediately and automatically shielded upon any further increase in the actuating pressure so that overstressing of said flexible wall or deformation thereof arising from further increase of pressure in the chamber l0 has been entirely avoided. Also the construction is such that immediately the pressure drops below that value at which the wall 52 is moved to its limit position the pressure of the trapped fluid inside of the shield acting on the larger effective area of the end wall of the shield will cause a prompt expansion of the bellows l2. The shield is of a simple construction that can be readily formed by stamping from sheet metal, and it may be readily secured in position by spinning as heretofore pointed out, so that the shielding provision is inexpensive and economical to fabricate and assemble.

While the embodiment of the invention illustrated on the drawing has been described with considerable particularity, it is to be expressly understood that this embodiment has been selected merely for the purpose of exemplifying the invention, and that as will now be apparent to those skilled in the art the invention may be embodied in a .variety of constructions and changes may be made in the details of construction, form, size, proportion, arrangement, etc., without departing from the spirit of this invention. Reference is therefore to be had to the appended claims for a definition of the invention.

What is claimed is:

1. In a pressure responsive device of the type including a rigid enclosure and a flexible expansible and collapsible corrugated wall disposed interiorly of said enclosure and forming therebetween an expansible and collapsible chamber to be subjected to fluid under pressure, said flexible wall having a movable end wall operatively connected to a means to be controlled, a cup-shaped imperforate shield mounted on said movable end wall and disposed in said expansible and collapsible chamber in surrounding relationship to said flexible wall, said cup-shaped shield being movable with said end wall under increase of pressure in said chamber to engage its free end in fluid sealing relation with said enclosure after a predetermined increase of pressure in said chamber to enclose and shield said flexible wall against further increase of pressure in said chamber,

said cup-shaped shield being provided on its peripheral wall with spaced axially extending outward projections cooperating with said enclosure to guide the movement of said shield and being constructed and arranged to preclude passage of fluid into the interior thereof when said free end thereof is in engagement with said enclosure.

2. In a pressure responsive device of the type including a rigid enclosing wall, an apertured plate coacting with the enclosing Wall to form a rigid enclosure, sealing means between the enclosing wall and the apertured plate, and a flexible expansible and collapsible corrugated Wall disposed interiorly of said enclosure and forming therebetween an expansible and collapsible chamber to be subjected to fluid under pressure, said flexible wall being secured at one end to said apertured plate and having a movable end wall adapted to be operatively connected to a means to be controlled, a member mounted on said movable end wall and disposed in said expansible and collapsible chamber, said member being movable with said movable end wall under increase of pressure in said chamber to engage said sealing means at a predetermined increase of pressure in said chamber to form a shielding enclosure for said flexible wall and being constructed and arranged to preclude passage of fluid into said enclosure when in engagement with said sealing means.

3. In a pressure responsive device of the type including a rigid enclosing wall, an apertured plate coacting with the enclosing wall to form a rigid enclosure, sealing means between the enclosing wall and the apertured plate, and a flexible expansible and collapsible corrugated wall disposed interiorly of said enclosure and forming therebetween an expansible and collapsible chamber to be subjected to fluid under pressure, said flexible wall being secured at one end to said apertured plate and having a movable end wall adapted to be operatively connected to a means to be controlled, a cup-shaped imperforate shield mounted on said movable end wall and disposed in said expansible and collapsible chamber in surrounding relationship to said flexible wall, said cup-shaped shield being movable with said end wall on increase of pressure in said chamber to engage said sealing means to effect a seal therewith and provide a fluid-tight enclosure for said flexible wall shielding said flexible wall against further increase or pressure in said chamber.

CHARLES D. BRANSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,593,115 Blauvelt July 20, 1926 2,058,858 Fetyko Oct. 27, 1936 2,154,901 Hulse Apr. 18, 1939 2,400,048 Jones May 7, 1946 2,470,288 Childs May 17, 1949 

